My team has been working through submitting an Alexa skill for certification. Our last submission was rejected for "The skill end-point is not accepting valid signed requests".
We have carefully looked over all requests we rejected and they all seem to fail for valid reasons based on the requirements https://developer.amazon.com/public/solutions/alexa/alexa-skills-kit/docs/developing-an-alexa-skill-...
We are using alexa-verifier https://www.npmjs.com/package/alexa-verifier There are no outstanding issues within the alexa-verifier project and searching the internet has not found anyone complaining about the same problem.
We opened Case# 2131329301 a week ago and have not received a response.